1. Field of the Invention
The present invention relates to a digital television, and more particularly, to an apparatus for automatically selecting an audio signal of a digital television which is capable of performing automatic input switching between an analog audio signal and a digital audio signal that are being inputted to a digital television.
2. Description of the Background Art
A digital television is typically designed to receive a video signal and an audio signal from various external sources such as a DVD player, an HD-DBS (high definition directly broadcast by satellite), a VGA (video graphics array). Especially, in case of an audio system signal, an analog audio signal and a digital audio signal are simultaneously inputted to the digital television.
FIG. 1 is an exemplary view of an audio signal selection apparatus of a digital television in accordance with a conventional art, which includes an analog/digital audio signal output unit 1 for outputting an analog audio signal of an L,R (analog audio) or a digital audio signal of a SPDIF (Sony Phillips Digital InterFace); and a digital television 2 for selecting the analog audio signal or the digital audio signal outputted from the analog/digital audio signal output unit 1 according to the state of an Input jack of SPDIF and processing the selected one.
The operation of the audio signal selecting apparatus of the digital television in accordance with the conventional art constructed as described above will now be explained in detail with reference to the accompanying drawings.
First, the analog/digital audio signal output unit 1 receives the analog audio signal (L, R) from an analog instrument and outputs it to the digital television 2.
The analog/digital audio signal output unit 1 receives a digital audio signal from a digital instrument such as a DVD player, a HD-DBS or a computer sound card and outputs it to the digital television 2. In this respect, the digital audio signal inputted to the analog/digital audio signal output unit 1 is transmitted to the Input jack of SPDIF of the digital television 2 through the SPDIF output jack such as the DVD player, HD-DBS or the computer sound card and the plug.
As stated above, the digital television 2 simultaneously receives the analog audio signal and the digital audio signal.
Accordingly, there is provided a menu to an A/V amplifier (not shown) of the digital television for users"" selection, from which a user can select either one of the analog audio signal and the digital audio signal for listening.
For example, when the user selects the analog audio signal, the digital television 2 receives and processes the analog audio signal, while if the user selects the digital audio signal, the digital television 2 receives and processes the digital audio signal.
In other way, the digital and the analog audio signal are processed in the following manner.
First, the digital television 2 checks the Input jack of SPDIF. Upon checking, in case that an RCA plug is put in the Input jack of SPDIF, the digital television 2 judges that a digital audio signal is being inputted, and automatically selects the digital audio signal to processes it. Meanwhile, if the RCA plug is not put in the Input jack of SPDIF, the digital television judges that an analog audio signal, rather than the digital audio signal, is being inputted, and automatically selects the analog audio signal to process it.
That is, it is mechanically judged that a plug is put in the input jack of the SPDIF and a high or a low voltage is transmitted to a CPU (not shown) of the digital television 2. Then, the CPU selects the digital audio signal as an input.
Likewise, whether or not the plug is in the Input jack of SPDIF is also mechanically judged and a low or a high voltage is transmitted to the CPU. Then, the CPU selects the analog audio signal as an input.
However, the audio signal selection apparatus of a digital television in accordance with a conventional art has the following problems.
First, since the judgement on whether the plug is put in the Input jack of SPDIF or not is made mechanically, even in case that no signal is inputted with the plug put in, the digital audio signal is selected and the user can not hear any sound.
Secondly, in a state that the plug is put in, if no digital audio signal is inputted, the plug that is put in the Input jack of SPDIF of the digital television must be removed in order for the user to hear the analog audio sound by the analog audio signal. Thus, this leads to a user""s inconvenience for use by forcing him or her to remove the plug.
Therefore, an object of the present invention is to provide an apparatus for automatically selecting an audio signal of a digital television which is capable of automatically switching an analog audio signal and a digital audio signal that are inputted to a digital television, and its method.
Another object of the present invention is to provide an apparatus and method for selecting digital audio signals which overcome the problems and limitation of the conventional art. To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided an apparatus for automatically selecting an audio signal of a digital television including: an amplifier for selectively receiving a digital audio signal among an analog audio signal and a digital audio signal that are being inputted, and amplifying it to a predetermined level; an integrating unit for detecting the level of the amplified signal and integrating it; and a controller for selecting a digital audio signal upon judgement that there is a digital audio signal if the integrated signal level is above a certain level, and outputting a control signal to select an analog audio signal upon judgement that there is no digital audio signal if the integrated signal level is below a certain level. As for the amplifier, an amplifier having a Schmitt-trigger characteristics is used.
In order to achieve the above objects, there is also provided a method for automatically selecting an audio signal of a digital television including the steps of: selectively receiving a digital audio signal among audio signals that are being inputted from at least two audio sources; integrating the digital audio signal as received and detecting its signal level; judging whether there is a digital audio signal according to the detected signal level; and performing automatic switching so that either one of the digital audio signal and the analog audio signal can be inputted depending on existence or nonexistence of the digital audio signal as judged.